Council working to reduce Heathcote flooding

Options for lessening the impacts of Heathcote River flooding are being discussed with the local community.

Staff involved in Christchurch City Council’s Land Drainage Recovery Programme have held two community meetings in Opawa this week to talk with residents about the work that is under way and the additional options being explored to reduce the risk of their properties flooding.

Options are being explored to lessen the impact of the Heathcote River flooding. 

The work under way includes:

• Dredging of the Woolston Cut. This work will start early next year and will remove the silt from the channel.
• Doing work to stabilise the Heathcote River’s banks. Work on the high priority areas is due to start in early 2018.
• Constructing four new storage basins in the Upper Heathcote area. Work on this $40 million project has already begun. The purpose of the storage basins is to store flood waters during the peak of a storm and slowly release them after water levels downstream have dropped. The additional storage basins will be able to hold 800,000 cubic metres of water and should reduce the risk of above-floor flooding for more than 100 properties in a one-in-50 year storm event.

The additional options being investigated by the Council include:

• Dredging the Heathcote River downstream of Hansen Park. Dredging will remove the silt that has built up in the river over the years and deepen the channel so it can handle bigger flows of water, lessening the likelihood of frequent floods.
• Using low stopbanks upstream of Hansen Park to reduce the risk of frequent underfloor flooding in the most vulnerable areas.
• Using the Council’s Flood Intervention Policy to help property owners whose homes frequently flood and are unlikely to benefit in a timely manner from planned flood mitigation works. That help might take the form of localised drainage works, housing raising, or in some cases the Council might offer to purchase the property.

Council Land Drainage Manager Keith Davison said floodplain management in the upper and lower Heathcote was a complex issue. There was no quick fix or silver bullet solution, but the proposed options would provide significant benefits and result in lower flood risk levels than prior to the earthquakes.

“The purpose of this week’s community meetings was to let residents know about the options we are looking at so we can start a discussion with them about where we go to from here,’’ Mr Davison said.

“We have some big decisions ahead of us which will have implications for the 2018-28 Long Term Plan. Staff are finalising an options report for the Council to consider next month.’’